The conversion of coal from a solid hydrogen deficient aromatic based material to a hydrogenated hydrocarbon of low molecular weight has been considered desirable for a long period of time because of the dwindling supplies of petroleum based hydrocarbons in this country and around the world and because of the large reserves of coal known to exist within this country. A process for the conversion of coal solids to liquid hydrocarbons, such as gasoline, would be extremely beneficial. Various methods for the conversion of coal to hydrocarbons have been suggested by the prior art including the direct conversion of coal by catalytic action and the solvent refining of coal by combined solvent and catalytic action.
This invention is directed to a coal conversion process of the latter type, namely a solvent refined coal recovery process. Particularly, the process involves the production of a catalyst for the hydrogenation of the solvent used in the coal conversion wherein the hydrogenation catalyst is of enhanced activity, of low cost and of no detriment to the depleted coal ash.
The prior art has recognized that metal sulfides have catalytic activity with respect to the hydrogenation of carbonaceous materials. A process for producing metal sulfides by the reaction of a metal or metal compound with hydrogen sulfide in the absence of hydrogen or oxygen atmospheres at a temperature range of 150.degree. to 700.degree. C. has been described in U.S. Pat. No. 2,127,383. Iron sulfides are contemplated in this patent, although they are not the preferred catalyst. The preferred reaction temperature ranges between 300.degree. C. and 600.degree. C.
Other attempts have been made to produce active hydrogenation catalysts from the reaction of metal oxides with hydrogen sulfide. Particularly, the reaction of iron oxides with hydrogen sulfide at a temperature range of 100.degree. C. to about 500.degree. C. is disclosed in U.S. Pat. No. 2,361,825. This patent is confined to the reduction of sulfur dioxide with hydrogen in the presence of the recited catalysts and does not contemplate carbonaceous material being hydrogenated.
It has been recognized that hydrogenation catalysts for coal are found in-situ in coal as a coal mineral impurity. Various metals and minerals are known to exist in coal, and at least some of these minerals, such as iron sulfide, have been reported to have activity in the conversion or hydrogenation of coal. Exemplary of such teachings is the article by Guin et al., "Effects of Coal Minerals on the Hydrogenation, Desulfurization and Solvent Extraction of Coal", Industrial Engineering Chemistry Process Design Development, Volume No. 2, 1978. This article identifies the mechanism by which coal solids are hydrogenated wherein a coal-derived solvent is first hydrogenated and the hydrogenated solvent then acts as a donor to provide hydrogen to the coal solids themselves. The hydrogenation of creosote oil as a solvent in a solvent refined coal process is specifically contemplated.
These prior art teachings identify the known catalytic effect of minerals and particularly iron sulfide in the hydrogenation of carbonaceous materials, such as coal and coal-derived solvents, to produce hydrocarbons similar to cracked petroleum products. However, the art does not disclose the surprising heightened catalytic activity of iron sulfide which is produced by a method wherein the temperature is confined to the range of 260.degree. C. to 315.degree. C. in a nonoxidizing atmosphere, or more specifically an optimal temperature of 275.degree. C. It is an object of the present invention to provide such a heightened active catalyst by a novel process which is incorporated into the hydrogenation process of a solvent refined coal production method.
It is a further object of present invention to provide such a process for the production of a hydrogenation catalyst of iron sulfide wherein the temperature is optimally maintained at 275.degree. C. during the catalyst preparation reaction period and the reaction is conducted in the absence of H.sub.2.
It is yet another object to provide a process wherein a hydrogen atmosphere exists during the catalyst preparation wherein the temperature is maintained at 350.degree. C.